(dogbane), a family of dicotyledonous plants. They are trees, shrubs, lianas, and subshrubs; less frequently, they are perennial herbs. The plants often contain a milky juice. The leaves are simple, entire, and generally opposite. The flowers, which are solitary or in inflorescences, are bisexual, regular, and usually five-lobed. The calyx often has internal glands. The corolla is usually tubular and twisted. There are more than 200 genera (over 2,000 species), distributed predominantly in the tropics and subtropics of both hemispheres. Important species in the USSR include dogbanes of the genus Apocynum, which yield fiber, and periwinkles of the genus Vinca and oleanders of the genus Nerium, which are cultivated as ornamentals. Many plants of this family are rubber plants (for example, Landolphia, Fun-tumia, and Clitandra); others yield valuable wood (Aspidos-perma), edible fruits (Carissa), tannins (quebracho), and dyes (Wrightia). Several plants, including those of the genera Rau-volfia and Strophantus, are poisonous and are used as medicinal plants.